Acrylic polyvinyl acetal films and composition

ABSTRACT

A film is described comprising a (meth)acrylic polymer and a polyvinyl acetal (e.g. butyral) resin. In some embodiments, the film has a glass transition temperature (i.e. Tg) ranging from 30° C. to 60° C. In some embodiments, the film has a gel content of at least 20% or greater. In some embodiments, the film has an elongation at break of at least 175%. The film typically comprises photoinitiator as a result of the method by which the film was made. The film may be a monolithic film or a layer of a multilayer film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International ApplicationPCT/US2015/064215, filed Jul. 12, 2015, which claims the benefit of U.S.Provisional Patent Application No. 62/088,945, filed Dec. 8, 2014, whichis incorporated herein by reference in its entirety.

SUMMARY

In one embodiment, a film is described. The film comprises a singlephase of (meth)acrylic polymer and a polyvinyl acetal resin. Thepolyvinyl acetal resin comprises polymerized units having the formula

wherein R₁ is hydrogen or a C1-C7 alkyl group. In one embodiment, thefilm has a glass transition temperature (i.e. Tg) ranging from 30° C. to60° C. In another embodiment, the film has gel content of at least 20%.In another embodiment, the film has an elongation at break of at least175%. The film typically comprises photoinitiator as a result of themethod by which the film was made. The film may be a monolithic film ora (e.g. exterior) layer of a multilayer film.

In another embodiment, a method of making a film is described. Themethod comprises providing a composition comprising polyvinyl acetalresin and free-radically polymerizable solvent monomer. The methodcomprises applying the composition to a substrate (e.g. release liner);polymerizing the solvent monomer; and optionally crosslinking thecomposition thereby forming a film. The polyvinyl acetal resin and typesand amounts of free-radically polymerizable solvent monomer are selectedsuch that the cured composition has a Tg ranging from 30° C. to 60° C.

In yet another embodiment, a composition is described comprising a(meth)acrylic polymer and a polyvinyl acetal resin. The compositionpreferably has a Tg ranging from 30° C. to 60° C.

In favored embodiments, the film and/or (e.g. radiation) polymerized andoptionally cured composition exhibits a suitable balance of (e.g. Tg,tensile, and/or elongation) properties such that it can be utilized as areplacement for polyvinyl chloride films or other types of (e.g.flexible) films.

DETAILED DESCRIPTION

Presently described are films and compositions comprising a(meth)acrylic polymer and polyvinyl acetal resin, as well as methods ofmaking. The composition is preferably prepared by dissolving polyvinylacetal resin in a free-radically polymerizable solvent monomer. Thesolvent monomer is preferably polymerized by exposure to (e.g.ultraviolet) radiation.

The film and composition comprises polymerized units of one or more(meth)acrylate ester monomers derived from a (e.g. non-tertiary) alcoholcontaining 1 to 14 carbon atoms and preferably an average of 4 to 12carbon atoms.

Examples of monomers include the esters of either acrylic acid ormethacrylic acid with non-tertiary alcohols such as ethanol, 1-propanol,2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol,2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-hexanol,2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol;3,5,5-trimethyl-1-hexanol, 3-heptanol, 1-octanol, 2-octanol,isooctylalcohol, 2-ethyl-1-hexanol, 1-decanol, 2-propylheptanol,1-dodecanol, 1-tridecanol, 1-tetradecanol, and the like.

The film and composition comprises polymerized units of one or more lowTg (meth)acrylate monomers, i.e. a (meth)acrylate monomer when reactedto form a homopolymer has a T_(g) no greater than 0° C. In someembodiments, the low Tg monomer has a T_(g) no greater than −5° C., orno greater than −10° C. The Tg of these homopolymers is often greaterthan or equal to −80° C., greater than or equal to −70° C., greater thanor equal to −60° C., or greater than or equal to −50° C.

The low Tg monomer may have the formulaH₂C═CR¹C(O)OR⁸wherein R¹ is H or methyl and R⁸ is an alkyl with 1 to 22 carbons or aheteroalkyl with 2 to 20 carbons and 1 to 6 heteroatoms selected fromoxygen or sulfur. The alkyl or heteroalkyl group can be linear,branched, cyclic, or a combination thereof.

Exemplary low Tg monomers include for example ethyl acrylate, n-propylacrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate,n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-methylbutylacrylate, 2-ethylhexyl acrylate, 4-methyl-2-pentyl acrylate, n-octylacrylate, 2-octyl acrylate, isooctyl acrylate (Tg=−70° C.), isononylacrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate,isotridecyl acrylate, octadecyl acrylate, and dodecyl acrylate.

Low Tg heteroalkyl acrylate monomers include, but are not limited to,2-methoxyethyl acrylate and 2-ethoxyethyl acrylate.

In some embodiments, the film and composition comprises polymerizedunits of at least one low Tg monomer(s) having an alkyl group with 6 to20 carbon atoms. In some embodiments, the low Tg monomer has an alkylgroup with 7 or 8 carbon atoms. Exemplary monomers include, but are notlimited to, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate,n-octyl (meth)acrylate, 2-octyl (meth)acrylate, isodecyl (meth)acrylate,and lauryl (meth)acrylate.

In some embodiments, the monomer is an ester of (meth)acrylic acid withan alcohol derived from a renewable source. A suitable technique fordetermining whether a material is derived from a renewable resource isthrough organic radiocarbon (¹⁴C) analysis according to ASTM D6866-10,as described in US2012/0288692. The application of ASTM D6866-10 toderive a “bio-based content” is built on the same concepts asradiocarbon dating, but without use of the age equations. The analysisis performed by deriving a ratio of the amount of organic radiocarbon(¹⁴C) in an unknown sample to that of a modern reference standard. Theratio is reported as a percentage with the units “pMC” (percent moderncarbon).

One suitable monomer derived from a renewable source is 2-octyl(meth)acrylate, as can be prepared by conventional techniques from2-octanol and (meth)acryloyl derivatives such as esters, acids and acylhalides. The 2-octanol may be prepared by treatment of ricinoleic acid,derived from castor oil, (or ester or acyl halide thereof) with sodiumhydroxide, followed by distillation from the co-product sebacic acid.Other (meth)acrylate ester monomers that can be renewable are thosederived from ethanol and 2-methyl butanol. In some embodiments, the filmand composition comprises a bio-based content of at least 10, 15, 20,25, 30, 35, 40, 45, 50, 55 or 60 wt.-% using ASTM D6866-10, method B.

The film and composition typically comprises at least 10, 15, 20 or 25wt.-% of polymerized units of monofunctional alkyl (meth)acrylate low Tgmonomer (e.g. having a Tg of less than 0° C.), based on the total weightof the polymerized units (i.e. excluding inorganic filler or otheradditives). As used herein, wt.-% of polymerized units refers to thewt.-% based on the total weight of the (meth)acrylic polymer, polyvinylacetal (e.g. butyral) resin, and crosslinker when present. The film andcomposition typically comprises no greater than 60, 55, 50, 45, or 40wt.-% of polymerized units of monofunctional alkyl (meth)acrylatemonomer having a Tg of less than 0° C., based on the total weight of thepolymerized units.

When the film or composition is free of unpolymerized components such asinorganic filler and additives, the wt.-% of specified polymerized unitsis approximately the same as the wt.-% of such polymerized units presentin the total composition. However, when the composition comprisesunpolymerized components, such as inorganic filler or otherunpolymerizable additives, the total composition can comprisesubstantially less polymerized units. In general, the total amount ofunpolymerizable additives may range up to 25 wt.-%. Thus, in the case offilms and composition comprising such unpolymerizable additives theconcentration of specified polymerized units can be as much as 5, 10,15, 20, 25 wt.-% less, depending on the total concentration of suchadditives. For example, when the film or composition comprises 20 wt.-%inorganic filler, the concentration of low Tg monofunctional alkyl(meth)acrylate monomer may be 20% less, i.e. at least 8 wt.-%, 12 wt.-%etc.

The film and composition generally comprise at least one (e.g.non-polar) high Tg monomer, i.e. a (meth)acrylate monomer when reactedto form a homopolymer has a Tg greater than 0° C. The high Tg monomermore typically has a Tg greater than 5° C., 10° C., 15° C., 20° C., 25°C., 30° C., 35° C., or 40° C.

In typical embodiments, the film and composition comprises at least onehigh Tg monofunctional alkyl (meth)acrylate monomers including forexample, t-butyl acrylate, methyl methacrylate, ethyl methacrylate,isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,s-butyl methacrylate, t-butyl methacrylate, stearyl methacrylate, phenylmethacrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornylmethacrylate, norbornyl (meth)acrylate, benzyl methacrylate, 3,3,5trimethylcyclohexyl acrylate, cyclohexyl acrylate, and propylmethacrylate or combinations.

In some embodiments, the film and composition comprises at least 1, 2,or 3 wt.-% up to 35 or 40 wt.-% of polymerized units of a monofunctionalalkyl (meth)acrylate monomer having a Tg greater than 40° C., 50° C.,60° C., 70° C., or 80° C. based on the total weight of the polymerizedunits (i.e. excluding inorganic filler or other additives). In someembodiments, the film and composition comprises no greater than 30, 25,20, or 10 wt.-% of polymerized units of high Tg monofunctional alkyl(meth)acrylate monomer. Further, in some embodiments, the film andcomposition comprises less than 1.0, 0.5, 0.1 wt.-% or is free ofpolymerized units of high Tg monofunctional alkyl (meth)acrylatemonomer.

The Tg of the homopolymer of various monomers is known and is reportedin various handbooks. The following table sets forth the Tg of someillustrative monomers as reported (unless specified otherwise) inPolymer Handbook, 4th edition, edited by J. Brandrup, E. H. Immergut,and E. A. Grulke, associate editors A. Abe and D. R. Bloch, J. Wiley andSons, New York, 1999.

Glass Transition Temperature (Tg) of the Homopolymer of Monomers Tg, °C. Tg, ° C. Methyl methacrylate   105 Methacrylic acid   223 Isobutylmethacrylate    53 2-hydroxyethyl acrylate    4 (b) Hexyl methacrylate −5 2-hydroxyethyl methacrylate    85 Methyl acrylate    10 N-vinylcarbazole   212 (a) Butyl acrylate  −54 N,N-dimethyl acrylamide    892-octyl acrylate  −45 N-vinyl pyrrolidone    54 2-ethylhexyl acrylate −50 N,N-Dimethylamino  −39 (a) ethyl acrylate Isobornyl acrylate    94N,N-Dimethylamino    19 ethyl methacrylate Acrylic acid   106 (a) I.Sideridou-Karayannidou and G. Seretoudi, Polymer, Vol. 40, Issue 17,1999, pp. 4915-4922. (b) B. Aran, M. Sankir, E. Vargun, N. D. Sankir,and A. Usanmaz; Journal of Applied Polymer Science, Wiley Periodicals,Inc., A Wiley Company, 2010, Vol. 116, pp. 628-635.

In typical embodiments, the film and composition further comprises atleast 10, 15 or 20 wt.-% and no greater than 65 wt.-% of polymerizedunits of polar monomers. Such polar monomers generally aids incompatibilizing the polyvinyl acetal (e.g. butyral) resin with the highand low Tg alkyl (meth)acrylate (e.g. solvent) monomers. The polarmonomers typically have a Tg greater than 0° C., yet the Tg may be lessthan the high Tg monofunctional alkyl (meth)acrylate monomer.

Representative polar monomers include for example acid-functionalmonomers, hydroxyl functional monomers, nitrogen-containing monomers,and combinations thereof.

In some embodiments, the film and composition comprises polymerizedunits of an acid functional monomer (a subset of high Tg monomers),where the acid functional group may be an acid per se, such as acarboxylic acid, or a portion may be salt thereof, such as an alkalimetal carboxylate. Useful acid functional monomers include, but are notlimited to, those selected from ethylenically unsaturated carboxylicacids, ethylenically unsaturated sulfonic acids, ethylenicallyunsaturated phosphonic acids, and mixtures thereof. Examples of suchcompounds include those selected from acrylic acid, methacrylic acid,itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleicacid, oleic acid, β-carboxyethyl (meth)acrylate, 2-sulfoethylmethacrylate, styrene sulfonic acid,2-acrylamido-2-methylpropanesulfonic acid, vinylphosphonic acid, andmixtures thereof.

Due to their availability, acid functional monomers are generallyselected from ethylenically unsaturated carboxylic acids, i.e.(meth)acrylic acids. When even stronger acids are desired, acidicmonomers include the ethylenically unsaturated sulfonic acids andethylenically unsaturated phosphonic acids. In some embodiments, thefilm and composition comprises 0.5 up to 20 or 25 wt.-% of polymerizedunits of acid functional monomers, such as acrylic acid. In someembodiments, the film and composition comprises at least 1, 2, 3, 4, or5 wt.-% of polymerized units of acid-functional monomers. In otherembodiments, the film and composition comprises less than 1.0, 0.5, 0.1wt.-% or is free of polymerized units of acid-functional monomers.

In some embodiments, the film and composition comprisesnon-acid-functional polar monomer.

One class of non-acid-functional polar monomers includesnitrogen-containing monomers. Representative examples includeN-vinylpyrrolidone; N-vinylcaprolactam; acrylamide; mono- or di-N-alkylsubstituted acrylamide; t-butyl acrylamide; dimethylaminoethylacrylamide; and N-octyl acrylamide. In some embodiments, the film andcomposition comprises at least 0.5, 1, 2, 3, 4, or 5 wt.-% ofpolymerized units of nitrogen-containing monomers and typically nogreater than 25 or 30 wt.-%. In other embodiments, the film andcomposition comprises less than 1.0, 0.5, 0.1 wt.-% or is free ofpolymerized units of nitrogen-containing monomers.

Another class of non-acid-functional polar monomers includesalkoxy-functional (meth)acrylate monomers. Representative examples2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate,2-hydroxyethyl (meth)acrylate, 2-(methoxyethoxy)ethyl, 2-methoxyethylmethacrylate, and polyethylene glycol mono(meth)acrylates.

In some embodiments, the film and composition comprises at least 0.5, 1,2, 3, 4, or 5 wt.-% of polymerized units of alkoxy-functional(meth)acrylate monomers and typically no greater than 30 or 35 wt.-%. Inother embodiments, the film and composition comprises less than 1.0,0.5, 0.1 wt.-% or is free of polymerized units of alkoxy-functional(meth)acrylate monomers.

Preferred polar monomers include acrylic acid, 2-hydroxyethyl(meth)acrylate; N,N-dimethyl acrylamide and N-vinylpyrrolidinone. Thefilm and composition generally comprises polymerized units of polarmonomer in an amount of at least 10, 15 or 20 wt.-% and typically nogreater than 65, 60, 55, 50 or 45 wt.-%.

The film and composition may optionally comprise vinyl monomersincluding vinyl esters (e.g., vinyl acetate and vinyl propionate),styrene, substituted styrene (e.g., α-methyl styrene), vinyl halide, andmixtures thereof. As used herein vinyl monomers are exclusive of polarmonomers. In some embodiments, the film and composition comprises atleast 0.5, 1, 2, 3, 4, or 5 wt.-% and typically no greater than 10 wt.-%of polymerized units of vinyl monomers. In other embodiments, the filmand composition comprises less than 1.0, 0.5, 0.1 wt.-% or is free ofpolymerized units of vinyl monomers.

In some favored embodiments, the polymerized units of the (meth)acrylicpolymer contain aliphatic groups and lack aromatic moieties.

In typical embodiments, the (e.g. solvent) monomer(s) are polymerized toform a random (meth)acrylic polymer copolymer.

The polyvinyl acetal resin utilized in the present invention isobtained, for example, by reacting polyvinyl alcohol with aldehyde, asknown in the art.

Polyvinyl alcohol resins are not limited by the production method. Forexample, those produced by saponifying polyvinyl acetate and the likewith alkali, acid, ammonia water, and the like, can be used. Polyvinylalcohol resins may be either completely saponified or partiallysaponified. It is preferable to use those having a saponification degreeof 80 mol % or more. The polyvinyl alcohol resins may be used singly orin combination of two or more.

Aldehydes used in the production of the polyvinyl acetal resin includeformaldehyde (including paraformaldehyde), acetaldehyde (includingparaacetaldehyde), propionaldehyde, butyraldehyde, n-octylaldehyde,amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde,cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde,2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde,p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde,β-phenylpropionaldehyde, and the like. These aldehydes may be usedsingly or in combination of two or more.

The polyvinyl acetal resin generally has repeating units represented byChemical Formula 1.

In Chemical Formula 1, n is the number of different types of aldehydeused in acetalization; R₁, R₂, . . . , R_(n), are independently a (e.g.C1-C7) alkyl residue of aldehyde used in the acetalization reaction, ora hydrogen atom; k₁, k₂, . . . , k_(n) are independently the proportionof each acetal unit containing R₁, R₂, . . . , R_(n), (molar ratio); lis the proportion of vinyl alcohol units (molar ratio); and m is theproportion of vinyl acetate units (molar ratio). The sum of k₁+k₂+ . . .+k_(n)+l+m=1. Further at least one of k₁, k₂, . . . , k_(n) may not bezero. When a single type of aldehyde is utilized in the preparation ofthe polyvinyl acetal resin, such single aldehyde may be represented byk₁. The number of repeat units of k₁+l+m is sufficient to provide thedesired molecular weight. In this embodiment, k₂ and k_(n) may be zero.The polyacetal resin is typically a random copolymer. However, blockcopolymers and tapered block copolymers may provide similar benefits asrandom copolymers.

The content of polyvinyl acetal (e.g. butyral) typically ranges from 65wt-% up to 90 wt-% of the polyvinyl acetal (e.g. butyral) resin. In someembodiments, the content of polyvinyl acetal (e.g. butyral) ranges fromabout 70 or 75 up to 80 or 85 wt.-%. Thus, the number of repeat units of“k₁, k₂, . . . , k_(n)” are selected accordingly.

The content of polyvinyl alcohol typically ranges from about 10 to 30wt-% of the polyvinyl acetal (e.g. butyral) resin. In some embodiments,the content of polyvinyl alcohol ranges from about 15 to 25 wt-%. Thus,“l” is selected accordingly.

The content of polyvinyl acetate can be zero or range from 1 to 8 wt.-%of the polyvinyl acetal (e.g. butyral) resin. In some embodiments, thecontent of polyvinyl acetate ranges from about 1 to 5 wt.-%. Thus, “m”is selected accordingly.

In some embodiments, the alkyl residue of aldehyde comprises 1 to 7carbon atoms. In other embodiments, the alkyl reside of the aldehydecomprises 3 to 7 carbon atoms such as in the case of butylaldehyde(R₁=3), hexylaldehyde (R₁=5), n-octylaldehyde (R₁=7). Of thesebutylaldehyde, also known as butanal is most commonly utilized.Polyvinyl butyral (“PVB”) resin is commercially available from Kurarayunder the trade designation “Mowital™” and Solutia under the tradedesignation “Butvar™”.

In some embodiments, the polyvinyl acetal (e.g. butyral) resin has a Tgranging from about 60° C. up to about 75° C. or 80° C. In someembodiments, the Tg of the polyvinyl acetal (e.g. butyral) resin is atleast 65 or 70° C. When other aldehydes, such as n-octyl aldehyde, areused in the preparation of the polyvinyl acetal resin, the Tg may beless than 65° C. or 60° C. The Tg of the polyvinyl acetal resin istypically at least 35, 40 or 45° C. When the polyvinyl acetal resin hasa Tg of less than 60° C., higher concentrations of high Tg monomers maybe employed in the film and (e.g. exemplified) composition in comparisonto those utilizing polyvinyl butyral resin. When other aldehydes, suchas acetaldehyde, are used in the preparation of the polyvinyl acetalresin, the Tg may be greater than 75° C. or 80° C. When the polyvinylacetal resin has a Tg of greater than 70° C., higher concentrations oflow Tg monomers may be employed in the film and (e.g. exemplified)composition in comparison to those utilizing polyvinyl butyral resin.

The polyvinyl acetal (e.g. PVB) resin typically has an average molecularweight (Mw) of at least 10,000 g/mole or 15,000 g/mole and no greaterthan 150,000 g/mole or 100,000 g/mole. In some favored embodiments, thepolyacetal (e.g. PVB) resin has an average molecular weight (Mw) of atleast 20,000 g/mole; 25,000; 30,000, 35,000 g/mole and typically nogreater than 75,000 g/mole.

The film and composition comprises 5 to 30 wt.-% of polyvinyl acetalresin such as polyvinyl butyral based on the total weight of thepolymerized units of the (meth)acrylate polymer, polyvinyl acetal (e.g.butyral) resin, and crosslinker when present. In some embodiments, thefilm and composition comprises at least 10, 11, 12, 13, 14, or 15 wt.-%of polyvinyl acetal (e.g. PVB) resin. In some embodiments, the film andcomposition comprises no greater than 25 or 20 wt-% of polyvinyl acetal(e.g. PVB) resin. When the film and composition comprises a polyvinylacetal (e.g. PVB) resin having an average molecular weight (Mw) lessthan 50,000 g/mole, the film and composition may comprise higherconcentration polyvinyl acetal (e.g. PVB) resin such as 35 or 40 wt.-%.Thus, the film and composition comprises a minor amount of polyvinylacetal (e.g. PVB) resin in combination with a major amount of(meth)acrylic polymer. The amount of (meth)acrylic polymer is typicallyat least 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 wt.-% of the film.

In some embodiments, the film and composition comprises a crosslinker.In some embodiments, the crosslinker is a multifunctional crosslinkercapable of crosslinking polymerized units of the (meth)acrylic polymersuch as in the case of crosslinkers comprising functional groupsselected from (meth)acrylate, vinyl, and alkenyl (e.g. C₃-C₂₀ olefingroups); as well as chlorinated triazine crosslinking compounds.

Examples of useful (e.g. aliphatic) multifunctional (meth)acrylateinclude, but are not limited to, di(meth)acrylates, tri(meth)acrylates,and tetra(meth)acrylates, such as 1,6-hexanediol di(meth)acrylate,poly(ethylene glycol) di(meth)acrylates, polybutadiene di(meth)acrylate,polyurethane di(meth)acrylates, and propoxylated glycerintri(meth)acrylate, and mixtures thereof.

In one embodiment, the crosslinking monomer comprises a (meth)acrylategroup and an olefin group. The olefin group comprises at least onehydrocarbon unsaturation. The crosslinking monomer may have the formula

R1 is H or CH₃,L is an optional linking group; andR2 is an olefin group, the olefin group being optionally substituted.

Dihydrocyclopentadienyl acrylate is one example of this class ofcrosslinking monomer. Other crosslinking monomers of this typecomprising a C₆-C₂₀ olefin are described in WO2014/172185.

In other embodiments, the crosslinking monomer comprises at least twoterminal groups selected from allyl, methallyl, or combinations thereof.An allyl group has the structural formula H₂C═CH—CH₂—. It consists of amethylene bridge (—CH₂—) attached to a vinyl group (—CH═CH₂). Similarly,a methallyl group is a substituent with the structural formulaH₂C═C(CH₃)—CH₂—. The terminology (meth)allyl includes both allyl andmethallyl groups. Crosslinking monomers of this types are described inPCT Publication WO2015/157350.

In some embodiments, the film and composition may comprise amultifunctional crosslinker comprising vinyl groups, such as in the caseof 1,3-divinyl tetramethyl disiloxane.

The triazine crosslinking compound may have the formula.

wherein R₁, R₂, R₃ and R₄ of this triazine crosslinking agent areindependently hydrogen or alkoxy group, and 1 to 3 of R₁, R₂, R₃ and R₄are hydrogen. The alkoxy groups typically have no greater than 12 carbonatoms. In favored embodiments, the alkoxy groups are independentlymethoxy or ethoxy. One representative species is2,4-bis(trichloromethyl)-6-(3,4-bis(methoxy)phenyl)-triazine. Suchtriazine crosslinking compounds are further described in U.S. Pat. No.4,330,590.

In other embodiments, the crosslinker comprises hydroxyl-reactivegroups, such as isocyanate groups, capable of crosslinking alkoxy groupof the (meth)acrylic polymer (e.g. HEA) or polyvinyl alcohol groups ofthe polyvinyl acetal (PVB). Examples of useful (e.g. aliphatic)multifunctional isocyanate crosslinkers include hexamethylenediisocyanate, isophorone diisocyanate, as well as derivatives andprepolymers thereof.

Various combinations of two or more of crosslinkers may be employed.

When present, the crosslinker is typically present in an amount of atleast 0.5, 1.0, 1.5, or 2 wt-% ranging up to 5 or 10 wt-% based on thetotal weight of the polymerized units of the (meth)acrylate polymer,polyvinyl acetal (e.g. butyral) resin, and crosslinker. Thus the filmand composition comprise such amount of polymerized crosslinker units.

The composition can be polymerized by various techniques, yet ispreferably polymerized by solventless radiation polymerization,including processes using electron beam, gamma, and especiallyultraviolet light radiation. In this (e.g. ultraviolet light radiation)embodiment, generally little or no methacrylate monomers are utilized.Thus, the film and composition comprises zero or no greater than 10, 9,8, 7, 6, 5, 4, 3, 2, or 1 wt-% of polymerized units of monomer having amethacrylate group. One method of preparing the film and compositiondescribed herein comprises dissolving the polyvinyl acetal (e.g. PVB)polymer resin in the unpolymerized solvent monomer(s) of the(meth)acrylic polymer forming a coatable composition of sufficientviscosity.

Another method includes partially polymerizing the solvent monomer(s) toproduce a syrup composition comprising a solute (meth)acrylic polymerdissolved in unpolymerized solvent monomer(s). The unpolymerized solventmonomer(s) typically comprise the same monomer(s) as utilized to producethe solute (meth)acrylic polymer. If some of the monomers were consumedduring the polymerization of the (meth)acrylic polymer, theunpolymerized solvent monomer(s) comprises at least some of the samemonomer(s) as utilized to produce the solute (meth)acrylic polymer.Further, the same monomer(s) or other monomer(s) can be added to thesyrup once the (meth)acrylic polymer has been formed. Partialpolymerization provides a coatable solution of the (meth)acrylic solutepolymer in one or more free-radically polymerizable solvent monomers.

A preferred method of preparation of the syrup composition isphotoinitiated free radical polymerization.

The polyvinyl acetal (e.g. PVB) polymer can be added prior to and/orafter partial polymerization of monomer(s) of the (meth)acrylic polymer.In this embodiment, the coating composition comprises partiallypolymerized (e.g. alkyl(meth)acrylate) solvent monomers and polyvinylacetal (e.g. PVB) polymer resin. The coatable composition is then coatedon a suitable substrate and further polymerized.

The viscosity of the coatable composition is typically at least 1,000 or2,000 cps ranging up to 100,000 cps at 25° C. In some embodiments, theviscosity is no greater than 75,000; 50,000, or 25,000 cps. The coatablecomposition is coated on a suitable substrate such as a release liner,and polymerized by exposure to radiation.

The method can form a higher molecular weight (meth)acrylic polymer thancan be used by solvent blending a prepolymerized (meth)acrylic polymerand polyvinyl acetal (e.g. PVB) polymer. Higher molecular weight(meth)acrylic polymer can increase the amount of chain entanglements,thus increasing cohesive strength. Also, the distance between crosslinkscan be greater with a high molecular (meth)acrylic polymer, which allowsfor increased wet-out onto a surface of an adjacent (e.g. film) layer.

The molecular weight of the composition can be increased even further bythe inclusion of crosslinker.

The high molecular weight (meth)acrylic polymer as well as thecomposition and film typically has a gel content (as measured accordingto the Gel Content Test Method described in the examples utilizingtetrahydrofuran (THF) of at least 20, 25, 30, 35, or 40%. In someembodiments, the gel content is at least 45, 50, 55, 60, 65, 70, 75, 80,85, 90, or 95%. The gel content is typically less than 100%, 99%, or98%. When the (meth)acrylic polymer has a high gel content, it istypically not thermoplastic.

The polymerization is preferably conducted in the absence ofunpolymerizable organic solvents such as ethyl acetate, toluene andtetrahydrofuran, which are non-reactive with the functional groups ofthe solvent monomer and polyvinyl (e.g. PVB) acetal. Solvents influencethe rate of incorporation of different monomers in the polymer chain andgenerally lead to lower molecular weights as the polymers gel orprecipitate from solution. Thus, the film and compositions can be freeof unpolymerizable organic solvent.

Useful photoinitiators include benzoin ethers such as benzoin methylether and benzoin isopropyl ether; substituted acetophenones such as2,2-dimethoxy-2-phenylacetophenone photoinitiator, available the tradename IRGACURE 651 or ESACURE KB-1 photoinitiator (Sartomer Co., WestChester, Pa.), and dimethylhydroxyacetophenone; substituted α-ketolssuch as 2-methyl-2-hydroxy propiophenone; aromatic sulfonyl chloridessuch as 2-naphthalene-sulfonyl chloride; and photoactive oximes such as1-phenyl-1,2-propanedione-2-(O-ethoxy-carbonyl)oxime. Particularlypreferred among these are the substituted acetophenones.

Preferred photoinitiators are photoactive compounds that undergo aNorrish I cleavage to generate free radicals that can initiate byaddition to the acrylic double bonds. The photoinitiator can be added tothe mixture to be coated after the polymer (e.g. syrup) has been formed,i.e., photoinitiator can be added to the composition. Such polymerizablephotoinitiators are described, for example, in U.S. Pat. Nos. 5,902,836and 5,506,279 (Gaddam et al.).

Such photoinitiators are typically present in an amount of from 0.1 to1.0 wt-%. Relatively thick coatings can be achieved when the extinctioncoefficient of the photoinitiator is low.

The compositions can be coated on a release liner using conventionalcoating techniques. For example, these compositions can be applied bymethods such as roller coating, flow coating, dip coating, spin coating,spray coating knife coating, and die coating. Coating thicknesses mayvary. The composition may be of any desirable concentration forsubsequent coating, but is typically 5 to 30, 35 or 40 wt-% polyvinylacetal polymer solids in (meth)acrylic solvent monomer. The desiredconcentration may be achieved by further dilution of the coatingcomposition. The coating thickness may vary depending on the desiredthickness of the (e.g. radiation) cured film.

The composition and the photoinitiator may be irradiated with activatingUV radiation to polymerize the monomer component(s). UV light sourcescan be of various types including relatively low light intensity sourcessuch as blacklights, which provide generally 10 mW/cm² or less (asmeasured in accordance with procedures approved by the United StatesNational Institute of Standards and Technology as, for example, with aUVIMAP UM 365 L-S radiometer manufactured by Electronic Instrumentation& Technology, Inc., in Sterling, Va.) over a wavelength range of 280 to400 nanometers; and relatively high light intensity sources such asmedium pressure mercury lamps which provide intensities generallygreater than 10 mW/cm², preferably 15 to 450 mW/cm². Intensities canrange from 0.1 to 150 mW/cm², preferably from 0.5 to 100 mW/cm², andmore preferably from 0.5 to 50 mW/cm². The monomer component(s) can alsobe polymerized with high intensity light sources as available fromFusion UV Systems Inc. UV light to polymerize the monomer component(s)can be provided by light emitting diodes, blacklights, medium pressuremercury lamps, etc. or a combination thereof.

When the film is a monolithic film, the thickness of the (e.g.radiation) cured film is typically at least 10, 15, 20, or 25 microns (1mil) to 500 microns (20 mils) thickness. In some embodiments, thethickness of the (e.g. radiation) cured film is no greater than 400,300, 200, or 100 microns. When the film is a film layer of a multilayerfilm, the multilayer film typically has the thickness just described.However, the thickness of the film layer comprising the (meth)acrylicpolymer and polyvinyl acetal, as described herein, may be less than 10microns.

In one embodiment, the film layer comprising the (meth)acrylic polymerand polyvinyl acetal resin as an exterior layer or in other words a skinlayer. A second film layer is disposed upon the skin layer. The secondfilm layer typically has a different composition than the skin layer. Inone embodiment, the second film layer comprises a (e.g. radiation) curedlayer comprising a (meth)acrylic polymer and polyvinyl acetal. However,the second film layer has a Tg less than 30° C., 25° C. or 20° C. Thesecond film layer may have improved thermal forming, thermal laminating,or thermal bonding properties relative to the skin layer. Suitablesecond film layers include those described in “Acrylic Polyvinyl AcetalFilms, Compositions, and Heat Bondable Articles”, U.S. Application No.62/088,963, PCT/US2015/064219; incorporated herein by reference.

In some embodiments, the thickness of the film may range up to 50, 100,or 150 mils. The (e.g. radiation) cured film may be in the form ofindividual sheets, particularly for a thickness of greater than 20 mils.The (e.g. thinner) cured film may be in the form of a roll-good.

In some embodiments, the film, film layer, as well as the composition of(meth)acrylic polymer, polyvinyl acetal (e.g. butyral), and crosslinkerwhen present is transparent having a transmission of visible light of atleast 90, 91, 92, 93, 94, or 95% as measured according to the testmethod described in the examples. In some embodiments, the clarity is atleast 90, 91, 92, 93, 94, or 95%. The transmission and clarity aretypically less than 100%. In some embodiments, the haze is less than 15%or 10%. In some embodiments, the haze is less than 9, 8, 7, 6, 5, 4, 3,or 2%. The haze may be at least 0.5%.

The composition and film may optionally contain one or more conventionaladditives. Additives include, for example, antioxidants, stabilizers,ultraviolet absorbers, lubricants, processing aids, antistatic agents,colorants, impact resistance aids, fillers, matting agents, flameretardants (e.g. zinc borate) and the like. When present, the amount ofadditive can be at least 0.1, 0.2, 0.3, 0.4, or 0.5 wt-% and ittypically no greater than 25, 20, 15, 10 or 5 wt-% of the totalcomposition and film.

In some embodiments, the compositions are free of plasticizer, tackifierand combinations thereof. In other embodiments, the film and compositioncomprise plasticizer, tackifier and combinations thereof in amount nogreater than 5, 4, 3, 2, or 1 wt-% of the total composition. From thestandpoint of tensile strength, it is preferable not to add a largeamount of tackifier or plasticizer.

In some embodiments, the composition comprises fumed silica. Fumedsilica, also known as pyrogenic silica, is made from flame pyrolysis ofsilicon tetrachloride or from quartz sand vaporized in a 3000° C.electric arc. Fumed silica consists of microscopic droplets of amorphoussilica fused into (e.g. branched) three-dimensional primary particlesthat aggregate into larger particles. Since the aggregates do nottypically break down, the average particle size of fumed silica is theaverage particle size of the aggregates. Fumed silica is commerciallyavailable from various global producers including Evonik, under thetrade designation “Aerosil,” Cabot under the trade designation“Cab-O-Sil,” and Wacker Chemie-Dow Corning. The BET surface area ofsuitable fumed silica is typically at least 50 m²/g, or 75 m²/g, or 100m²/g. In some embodiments, the BET surface area of the fumed silica isno greater than 400 m²/g, or 350 m²/g, or 300 m²/g, or 275 m²/g, or 250m²/g. The fumed silica aggregates preferably comprise silica having aprimary particle size no greater than 20 nm or 15 nm. The aggregateparticle size is substantially larger than the primary particle size andis typically at least 100 nm or greater.

The concentration of (e.g. fumed) silica can vary. In some embodiments,the composition comprises at least 0.5 or 1.0 wt-% of (e.g. fumed)silica.

In some embodiments, the film and composition comprise colorants such aspigments and dyes such as titania and carbon black. The concentration ofsuch pigments and dyes can range up to about 20 wt-% of the totalcomposition.

The inclusion of inorganic oxides such as (e.g. fumed) silica andtitania can increase the tensile strength of the film and composition.

The film and (e.g. radiation) cured composition can be characterizedusing various techniques. Although the Tg of a copolymer may beestimated by use of the Fox equation, based on the Tgs of theconstituent monomers and the weight percent thereof, the Fox equationdoes not take into effect interactions, such as incompatibility, thatcan cause the Tg to deviate from the calculated Tg. The Tg of the filmand composition described refers to the midpoint Tg as measured byDifferential Scanning calorimetry, (DSC), according to the test methoddescribed in the examples. When the film and (e.g. radiation) curedcomposition comprises a monomer having a Tg greater than 150° C., theupper limit of the DSC testing temperature is chosen to be higher thanthat of the highest Tg monomer. The Tg of the film and (e.g. radiation)cured composition generally ranges from 30° C. to 55, 56, 57, 58, 59, or60° C. Thus, with respect to Tg, the film and (e.g. radiation) curedcomposition can be characterized as hard and glassy at room temperature(e.g. 25° C.), yet can be flexible. In some favored embodiments, the Tgof the film and (e.g. radiation) cured composition is at least 31, 32,33, 34, or 35° C. In other embodiments, the Tg of the film and (e.g.radiation) cured composition is at least 36, 37, 38, 39, or 40° C. Inyet other embodiments, the Tg of the film and (e.g. radiation) curedcomposition is at least 41, 42, 43, 44, or 45° C. The film and (e.g.radiation) cured composition preferably exhibits a single Tg as measuredby DSC. Thus, the polymerized (meth)acrylic polymer and polyvinyl acetalpolymer composition alone or in combination with crosslinker can exhibita single Tg. The midpoint Tg as measured by DSC of the film and (e.g.radiation) cured compositions described herein is 10-12° C. lower thanthe peak temperature Tg as measured by Dynamic Mechanical Analysis (DMA)at a frequency of 10 Hz and a rate of 3° C./min. Thus, a Tg of 60° C. asmeasured according to DSC is equivalent to 70-72° C. when measuredaccording to DMA as just described.

A single Tg is one indication of a single (e.g. continuous) phasemorphology. Thus, the film, as well as the polymerized (meth)acrylicpolymer and polyvinyl acetal polymer composition alone or in combinationwith crosslinker can be characterized as a single (e.g. continuous)phase. Alternatively, the film or (e.g. radiation) cured composition canbe tested by transmission electron microscopy (TEM) according to thetest method described in the examples. Single (e.g. continuous) phasemorphology is preferred for films having low haze and high transmission.

In other embodiments, the film, as well as the polymerized (meth)acrylicpolymer and polyvinyl acetal polymer composition alone or in combinationwith crosslinker can be characterized as having a dispersed phase ofpolyvinyl acetal (e.g. butyral) in a continuous phase of (meth)acrylicpolymer. The average dispersion size can be calculated by averaging thediameter of randomly chosen particles (e.g. 100 particles) of thedispersed phase utilizing TEM. The average dispersion size can rangefrom 0.1 to 10 microns. In some embodiments, the average dispersion sizeis less than 0.5, 0.3, 0.4, 0.3, 0.1 microns. An average dispersion sizeof less than 0.1 micron can also provide films having a low haze andhigh transmission.

The film and (e.g. radiation) cured composition can be characterized bytensile and elongation according to the test method described in theexamples. In favored embodiments, the tensile strength is at least 10,11, 12, 13, 14 or 15 MPa and typically no greater than 50, 45, 40, or 35MPa. The elongation at break can ranges from 2, 3, 4 or 5% up to about150%, 200% or 300% and greater. In some embodiments, the elongation isat least 50, 100, 150, or 175% and may range up to 225, 250, 275, or300%. In some embodiments, the conformability as determined by % tensileset of the film and (e.g. radiation) cured composition is at least 20,25, or 30%. In some embodiments, the film is suitable for use as areplacement for polyvinyl chloride film.

The film and (e.g. radiation) cured compositions are preferablynon-tacky to the touch at room temperature (25° C.) and preferably at(e.g. storage or shipping) temperatures ranging up to (120° F.) 50° C.In some embodiments, the films may exhibit a low level of adhesion toglass. For example, the 180° peel values can be about 2 oz/inch or lessat a 12 inch/minute peel rate.

The “Dahlquist Criterion for Tack” is widely recognized as a necessarycondition of a pressure sensitive adhesives (PSA). It states that a PSAhas a shear storage modulus (G′) of less than 3×10⁶ dyne/cm² (0.3 MPa)at approximately room temperature (25° C.) and a frequency of 1 Hz(Pocius, Adhesion and Adhesive Technology 3rd Ed., 2012, p. 288).

A shear storage modulus can be converted to a tensile storage modulususing the following equation: E′=2G′(r+1), where r is Poisson's ratiofor the relevant material. Using this equation and given that Poisson'sratio of elastomers and PSAs is close to 0.5, the Dahlquist Criterionexpressed as a tensile storage modulus (E′) is less than 0.9 MPa (9×10⁶dyne/cm²).

The film and (e.g. radiation) cured compositions described hereingenerally have a tensile storage modulus (E′) at 25° C. of greater than9×10⁶ dynes/cm² at 1 Hz as can be measured by dynamic mechanicalanalysis (as determined by the test method described in the examples).The tensile storage modulus (E′) at 25° C. is usually greater than 1×10⁷dynes/cm² (1 MPa), 5×10⁷ dynes/cm², 1×10⁸ dynes/cm², 5×10⁸ dynes/cm²,1×10⁹ dynes/cm², 5×10⁹ dynes/cm², or 1×10¹⁰ dynes/cm² (i.e. 1000 MPa) at1 Hz. Thus, the film and composition is not a pressure sensitiveadhesive in accordance with the Dahlquist criteria.

Herein, “(meth)acryloyl” is inclusive of (meth)acrylate and(meth)acrylamide.

Herein, “(meth)acrylic” includes both methacrylic and acrylic.

Herein, “(meth)acrylate” includes both methacrylate and acrylate.

The term “alkyl” includes straight-chained, branched, and cyclic alkylgroups and includes both unsubstituted and substituted alkyl groups.Unless otherwise indicated, the alkyl groups typically contain from 1 to20 carbon atoms. Examples of “alkyl” as used herein include, but are notlimited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl,t-butyl, isopropyl, n-octyl, 2-octyl, n-heptyl, ethylhexyl, cyclopentyl,cyclohexyl, cycloheptyl, adamantyl, and norbomyl, and the like. Unlessotherwise noted, alkyl groups may be mono- or polyvalent.

The term heteroalkyl refers to an alkyl group, as just defined, havingat least one catenary carbon atom (i.e. in-chain) replaced by a catenaryheteroatom such as O, S, or N.

“Renewable resource” refers to a natural resource that can bereplenished within a 100 year time frame. The resource may bereplenished naturally or via agricultural techniques. The renewableresource is typically a plant (i.e. any of various photosyntheticorganisms that includes all land plants, inclusive of trees), organismsof Protista such as seaweed and algae, animals, and fish. They may benaturally occurring, hybrids, or genetically engineered organisms.Natural resources such as crude oil, coal, and peat which take longerthan 100 years to form are not considered to be renewable resources.

When a group is present more than once in a formula described herein,each group is “independently” selected unless specified otherwise.

The invention includes but is not limited to the following embodiments:

Embodiment 1 is a film comprising (meth)acrylic polymer and polyvinylacetal resin comprising polymerized units having the following formula

wherein R₁ is hydrogen or a C1-C7 alkyl group;wherein the film has a Tg ranging from 30° C. to 60° C.

Embodiment 2 is a film comprising (meth)acrylic polymer and polyvinylacetal resin comprising polymerized units having the following formula

wherein R₁ is hydrogen or a C1-C7 alkyl group;wherein the film has a gel content of at least 20%.

Embodiment 3 is the film of embodiment 2 wherein the film has a Tgranging from 30° C. to 60° C.

Embodiment 4 is a film comprising:

(meth)acrylic polymer and polyvinyl acetal resin comprising polymerizedunits having the following formula

wherein R₁ is hydrogen or a C1-C7 alkyl group;wherein the film has an elongation at break of at least 175%, a tensileset of at least 30%, or a combination thereof.

Embodiment 5 is the film of embodiment 4 wherein the film has a gelcontent of at least 20%.

Embodiment 6 is the film of embodiment 4 and/or 5 wherein the film has aTg ranging from 30° C. to 60° C.

Embodiment 7 is a method of making a film comprising:

a) providing a composition comprising

i) polyvinyl acetal resin comprising polymerized units having thefollowing formula

wherein R₁ is hydrogen or a C1-C7 alkyl group; and

ii) free-radically polymerizable solvent monomer comprisingalkyl(meth)acrylate monomer;

-   b) applying the composition to a substrate; and-   c) polymerizing the solvent monomer and optionally crosslinking the    composition thereby forming a composition wherein the composition is    characterized by a Tg ranging from 30° C. to 60° C., a gel content    of at least 20%, and elongation of at least 175%, or a combination    thereof.

Embodiment 8 is a composition comprising a (meth)acrylic polymer andpolyvinyl acetal resin comprising polymerized units having the followingformula

wherein R₁ is hydrogen or a C1-C7 alkyl group;

-   wherein the composition is characterized by a Tg ranging from 30° C.    to 60° C., a gel content of at least 20%, and elongation of at least    175%, or a combination thereof.

Embodiment 9 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises at least10, 15, 20 or 25 wt-% of polymerized units of monofunctional alkyl(meth)acrylate monomer having a Tg of less than 0° C.

Embodiment 10 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises nogreater than 60 wt-% of polymerized units of monofunctional alkyl(meth)acrylate monomer having a Tg of less than 0° C.

Embodiment 11 is embodiment 9 and/or 10 wherein the monofunctional alkyl(meth)acrylate monomer has a Tg of less than −10° C., −20° C., −30° C.,or −40° C.

Embodiment 12 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises abio-based content of at least 10, 15, 20 or 25% of the total carboncontent.

Embodiment 13 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprisespolymerized units of an alkyl (meth)acrylate monomer having an alkylgroup with 8 carbon atoms.

Embodiment 14 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises up to 35wt-% of polymerized units of a monofunctional alkyl (meth)acrylatemonomer having a Tg greater than 40° C., 50° C., 60° C., 70° C., or 80°C.

Embodiment 15 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises at least10, 15 or 20 wt-% and no greater than 65 wt-% of polymerized units ofpolar monomers.

Embodiment 16 is embodiment 15 wherein the polar monomers are selectedfrom acid-functional, hydroxyl functional monomers, nitrogen-containingmonomers, and combinations thereof.

Embodiment 17 is any of the previous embodiments wherein the polyvinylacetal resin comprises polyvinyl butyral.

Embodiment 18 is any of the previous embodiments wherein the film, (e.g.polymerized) composition of the method, or composition comprises 5 to 30wt-% of polyvinyl acetal resin.

Embodiment 19 is any of the previous embodiments wherein the polyvinylacetal resin has a polyvinyl alcohol content ranging from 10 to 30.

Embodiment 20 is any of the previous embodiments wherein the polyvinylacetal resin has a glass transition temperature ranging from 60° C. to75° C.

Embodiment 21 is any of the previous embodiments wherein the polyacetalresin has an average molecular weight (Mw) ranging from 20,000 g/mole to75,000 g/mole.

Embodiment 22 is any of the previous embodiments wherein the film,polymerized and crosslinked composition of the method, or compositioncomprises polymerized units of a multifunctional crosslinker wherein thecrosslinker comprises functional groups selected from (meth)acrylate,alkenyl, and hydroxyl-reactive groups.

Embodiment 23 is any of the previous embodiments wherein the film,composition of the method, or composition further comprises additives inan amount no greater than 25 wt-%.

Embodiment 24 is any of the previous embodiments wherein the film,composition of the method, or composition comprises photoinitiator.

Embodiment 25 is any of the previous embodiments wherein the film,polymerized composition of the method, or composition comprises nogreater than 10 wt-% of polymerized units of methacrylate monomers.

Embodiment 26 is any of the previous embodiments wherein the(meth)acrylic polymer is a random copolymer.

Embodiment 27 is any of the previous film embodiments wherein the filmis a monolithic film.

Embodiment 28 is any of the previous film embodiments wherein the filmis a film layer of a multilayer film.

Embodiment 29 is the multilayer film of Embodiment 28 further comprisinga second film layer, the second film layer comprising a (meth)acrylicpolymer and polyvinyl acetal resin wherein the second film layer has aTg of less than 30° C.

Embodiment 30 is the multilayer film of Embodiment 28 wherein the secondfilm layer is heat bondable.

Objects and advantages of this invention are further illustrated by thefollowing examples. The particular materials and amounts, as well asother conditions and details, recited in these examples should not beused to unduly limit this invention.

TABLE 1 Materials Abbreviation Description PVB B60H Poly(vinyl butyral),available from Kuraray, Houston, TX, under the trade designation“MOWITAL B60H” (Tg = 70° C.) Low Tg Monomers 2-OA 2-Octyl acrylate,Prepared according to Preparatory (Tg = −45° C.) Example 1 of U.S. Pat.No. 7,385,020 2-EHA 2-Ethylhexyl acrylate, available from BASF, Florham(Tg = −50° C.) Park, NJ IOA Iso-octyl acrylate, obtained from 3MCompany, St. (Tg = −70° C.) Paul, MN. High Tg Monomers AA Acrylic acid,available from BASF, Florham Park, NJ. (Tg = 106° C.) CD 9055 acidacrylate, available from Sartomer, Exton, PA, (Tg = <30° C.) under thetrade designation “CD 9055” IBOA Isobornyl acrylate, available from SanEsters, New (Tg = 94° C.) York, NY NNDMA N,N-Dimethyl Acrylamide,available from TCI (Tg = 89° C.) America, Montgomeryville, PA NVPN-vinylpyrrolidone, available from TCI America, (Tg = 54° C.)Montgomeryville, PA HEA 2-Hydroxyl ethyl acrylate, available from BASF(Tg = 4° C.) Crosslinkers HDDA 1,6-Hexanediol diacrylate, available fromAllnex, USA DPA Dicyclopentadienyl acrylate, available from Monomer-Polymer Laboratories, Philadelphia, PA CN963B80 An aliphatic polyesterbased urethane diacrylate oligomer blended with 20% SR238, hexane dioldiacrylate available from Sartomer, Exton, PA, under the tradedesignation “CN 963 B80” CN965 An aliphatic polyester based urethanediacrylate oligomer available from Sartomer, Exton, PA, under the tradedesignation “CN 965” DESMODUR ™ An NCO prepolymer based on XP 2617hexamethylene diisocyanate, available from Bayer MaterialScience,Pittsburgh, PA, under the trade designation “DESMODUR XP 2617”DESMODUR ™ Trifunctional crosslinker based on hexamethylene N3600diisocyanate, available from Bayer Material Science, Pittsburgh, PA,under the trade designation “DESMODUR N3600” DESMODUR ™ A polyetherprepolymer based on isophorone VP LS 2371 diisocyanate available fromBayer Material Science, Pittsburgh, PA, under the trade designation“DESMODUR XP2371” Other Components H15 silica Fumed silica, availablefrom Wacker, under the trade designation “WACKER H15” PARAPLEX Polymericester plasticizer, available from Hallstar, A-8600 Chicago, IL, underthe trade designation “PARAPLEX Plasticizer A-8600” Carbon black Carbonblack, available from Birla Carbon under the Pigment trade designation“RAVEN 14 CARBON BLACK” TiO₂ Pigment Titanium dioxide, available fromKronus, Inc., Dallas, TX Zinc borate Zinc borate, available from RioTinto. Flame Retardant IRG 651 Initiator, available from BASF, FlorhamPark, NJ, under the trade designation “IRGACURE 651” IRG 819 Initiator,available from BASF, Florham Park, NJ, under the trade designation“IRGACURE 819”Test MethodsTensile Strength and Elongation Test

Tensile and elongation testing was conducted according to ASTM D882-10(unless specified otherwise) utilizing an INSTRON MODEL 4500 UNIVERSALTESTING SYSTEM with a 1 kN load cell. Testing was performed at a rate of300 mm/minute (11.81 inches/minute) for a total distance of 250 mm (9.84inches). Samples were tested at least 24 hours after being prepared. A0.5″ (˜1.3 cm) wide strip of film was cut, and the thickness wasdetermined for each sample using a micrometer. Typical sample length was5-7 cm (2-3 inches). Test results were reported as the average of 3-5sample replicates. The tensile strength (nominal) and percent elongationat break were determined, as described by 11.3 and 11.5 of ASTM D882-10.

Differential Scanning Calorimetry (DSC)

Approximately 5 mg of each of the film samples were placed in individualstandard aluminum DSC pans (Thermal Analysis T080715) and placed in theautosampler of a differential scanning calorimeter (TA DSC Q200, TAInstruments). For each sample analysis, pans were individually placed onone of the differential posts in the calorimeter's enclosed cell, alongwith an empty reference pan on the opposite post. The temperature wasraised to 150° C., cooled to −50° C., and reheated a second time to+150° C., at rates of 5° C./min. The second heating cycle was used todetermine the Tg, referring to the midpoint temperature, described asT_(mg) in ASTM D3418-12.

Gel Content

Aluminum pans were weighed and the weights (W1) were recorded. Meshbaskets were placed in pans and then weighed (basket and pan) and theweights (W2) were recorded. One inch (2.54 centimeter) diameter adhesivesamples were placed into the baskets, and the samples (pan, basket, andadhesive sample) were weighed again (W3) and recorded. Samples (basketsand adhesive sample) were then placed in glass jars, covered withtetrahydrofuran, and left for three days. Then, the samples (basket andadhesive sample) were removed from tetrahydrofuran, and placed back intopans. Samples (pan, basket, and adhesive samples) were placed in an ovenat 120° C. for 2 hours. Samples were removed from the oven and allowedto cool. Subsequently, samples were weighed and the weights (W4) wererecorded. % Gel content=100(W4−W2)/(W3−W2).

Conformability

Conformability was evaluated using a tensile set test method accordingto ASTM D412-6a^(e2): “Standard Test Methods for Vulcanized Rubber andThermoplastic Elastomers—Tension” as follows. Test specimens having awidth of 2.54 cm (1 inch) and a length of 10.2 cm (4 inches) wereemployed. The initial jaw separation distance on the film test specimen(50.8 mm) was marked, then the specimen was stretched at a rate of was304.8 mm/minute (12 inches/minute) to 50% greater than its originallength (76.2 mm) and held for 30 seconds. The test specimen was thenreleased from the jaw grips and after 24 hours (or other specifiedduration of time) the length between the original marks was remeasured.Conformability, as measured by percent tensile set, was calculated as:% Tensile Set=[(L24−L0)/(L1−L0)]×100where L24 is the measured length after 24 (or other specified durationof time) hours, L0 is the initial jaw separation distance, and L1 is the50% extended length. A tensile set value of 100% corresponds to zeroelastic recovery. A film having such a value will remain in a stretchedposition without contracting.Acrylic Polymer Control Examples

Control Example A and B were made by charging a quart jar with 2-OA,IBOA, and AA or NNDMA as indicated in Table 2. The monomer mixture wasdegassed at −20 inches of mercury (−6.8 kPa) for 5 minutes and purgedwith nitrogen for 5-10 minutes then exposed to low intensity UV A lightradiation (less than 10 mW/cm², referred to as UV A because the outputis primarily between 320 and 390 nm with a peak emission at around 350nm which is in the UV A spectral region) until a coatable prepolymersyrup was prepared.

0.09 wt-% of IRG 651 photoinitiator and 0.02 wt-% of HDDA crosslinkerwas added to the coatable prepolymer syrup of Control Example A. 0.21wt-% of IRG 651 photoinitiator was added to the coatable prepolymersyrup of Control Example B.

Control Examples A and B were coated at a thickness ranging from about1.5 to 12 mils between untreated PET liners and under a nitrogenatmosphere cured by further exposure to UVA light. The total energy wasmeasured using a Powermap™ radiometer equipped with a low intensitysensing head (available from EIT Inc., Sterling, Va.) and was 1824mJ/cm² for each of these control samples.

The concentration of the monomers in the cured Control Examples A and Bwere as follows:

TABLE 2 Control 2-OA IBOA AA HDDA Example A 39.94% 54.92% 4.99% 0.02%Control 2-OA IBOA NNDMA Example B 44.89% 24.94% 29.93%

EXAMPLES 1-13

Mixtures of monomers, PVB polymer, and other components were added toquart jars. The jars and contents were placed in a MAX 20 WHITESPEEDMIXER (available from FleckTek, Inc., Landrum, S.C.) and mixed at3500 RPM for 1 minute. The mixture was degassed at −20 inches of mercury(−6.8 kPa) for 5 minutes.

IRG 651 photoinitiator in an amount ranging from about 0.15 to 0.25 wt-%was added. The mixtures of Examples 1-13 were coated at a thicknessranging from about 1.5 to 12 mils between untreated PET liners and undera nitrogen atmosphere cured by exposure to a UV-A light source having aUV-A maximum in the range of 350-400 nm for 228 seconds. The totalenergy was measured using a Powermap™ radiometer equipped with a lowintensity sensing head (available from EIT Inc., Sterling, Va.) and was1824 mJ/cm² for each of these examples.

The wt-% of each type of polymerized unit in the cured films for each ofthe examples is reported in Tables 4A and 4B. The wt-% of polymerizedunits is slightly less than 100%. This difference is the photoinitiatorcontent. Although the photoinitiator is present in the film, theconcentration can be less than the amount initially added. When the filmcontained an additive, the amount of polymerized components incombination with the additive totaled 100%. Thus, Ex. 6 contained 14.48wt-% of TiO₂ and 85.52 wt-% of polymerized components. Of the 85.52 wt-%of polymerized components, 30.96 wt-% was 2-EHA. The polymerizedcomponents (excluding the additive) contained the wt-% of monomer, PVBpolymer, and crosslinker set forth in Tables 4A and 4B.

Preparation of Control C

An acrylic polymer was formed by UV polymerizing the components of thefollowing Table 3:

TABLE 3 2-EHA IBOA NVP AA 48 13.3 32 6.5

The acrylic polymer was then fed into a twin screw extruder, which washeated to 204° C. MOWITAL B60H was fed into the extruder at 20% byweight relative to the weight of the acrylic polymer. The polymermixture was extruded onto an untreated PET liner using a drop die. Thewt-% of the polymerized units of Control C is set forth in Table 4B.

TABLE 4A Wt.-% of Polymerized Units in Film Composition High Tg NitrogenLow Monomer Polar Polar PVB Ex. Tg Monomer IBOA Monomer Monomer B60HCrosslinker *Additive 1 2-OA 19.95 NNDMA 20 35.91 23.94 2 2-OA 19.96NNDMA 19.96 H15 silica 35.93 23.95 1.06 3 2-OA 18.36 NNDMA CD9055 18.35CN963B80 Paraplex 33.03 22.05 5.59 2.39 A8600 0.60 4 2-OA 19.43 NNDMACD9055 19.42 CN963B80 Zinc 34.95 23.33 0.11 2.53 Borate 4.82 5 2-EHA8.32 AA 16.64 CN963B80 30.08 18.62 2.64 HEA Desmodur 21.01 XP2617 2.53 62-EHA 8.57 AA 17.13 CN963B80 TiO₂ 30.96 16.29 2.71 14.48 HEA Desmodur21.63 XP2617 2.54

TABLE 4B Wt.-% of Polymerized Units in Film Composition High Tg NitrogenLow Tg Monomer Polar Polar PVB Ex. Monomer IBOA Monomer Monomer B60HCrosslinker Additive 7 2-EHA 8.53 AA 17.07 CN963B80 Carbon 30.84 16.312.70 Black HEA Desmodur 0.84 21.55 XP2617 2.84 8 2-EHA 8.73 AA 17.46CN963B80 31.55 17.29 2.77 HEA 22.04 9 2-EHA 2.8 NVP AA 13.6 CN963B80TiO₂ 20.3 13.6 10.2 2.0 11.5 HEA Desmodur 22.0 XP2371 15.6 10 2-EHA 2.8NVP AA 13.6 CN963B80 TiO₂ 20.3 13.6 10.2 2.0 11.5 HEA Desmodur 22.0N3600 15.6 11 2-EHA 10.2 AA 13.6 DPA 36.9 4.2 2.9 HEA 25.8 12 24 32 AA16.8 7.0 0.2 10 CN965 Irganox HEA 651 10 13 2-EHA 10.4 NVP 20.8 6.0 0.237.5 25 C93B80 Irganox 651 Control C 2-EHA 10.64 NVP AA 20.00 38.4025.60 5.20

Control F was a 50/50 mixture by weight of 50,000 g/mole molecularweight polymethylmethacrylate and PVB(B60H).

Control G was a 50/50 mixture by weight of 350,000 g/mole molecularweight polymethylmethacrylate and PVB(B60H).

The films were subjected to DSC as well as Tensile Strength andElongation at Break testing, as previously described. The results arereported in Table 5.

TABLE 5 Tensile Strength Elongation % Gel Example Tg (° C.) (MPa) atBreak Content Control A 26.9 12.3 186% NM (no PVB) Control B 17.5 11.0300% NM (no PVB) 1 38.9 19.4 299% 71 2 42.9 20.7 175% NM 3 36.6 19.8179% NM 4 35 18.3 176% 84 5 35.4 24.4 159% NM 6 38 21.5 152% 95 7 30.512.0 156% NM 8 36.5 34.3 205% 95 9 49 19.7 172% 93 10 57.9 38.9  7% 9511 53.5 27.6 200% 94 12 41.9 30.3 210% 85 13 51.9 25.3 211 37.5 ControlC 29.3 3.6  55% NM Control F NM NM NM 4.0 Control G NM NM NM 0 NM—NotMeasured

Example 7 was analyzed by Dynamic Mechanical Analysis (DMA) using aDMAQ800 from TA Instruments in tensile mode to characterize the physicalproperties of each sample as a function of temperature. Rectangularsamples, 6.2 mm wide and 0.05-0.07 mm thick, were clamped into the filmtension clamps of the instrument at 17-19 mm length. The furnace wasclosed and the temperature was equilibrated at −50° C. and held for 5minute. The temperature was then ramped from −50° C. to 50° C. at 3°C./min while the sample was oscillated at a frequency of 10 Hertz and aconstant strain of 0.1 percent. While many physical parameters of thematerial were recorded during the temperature ramp, tensile storagemodulus (E′) at 25° C. was recorded as 1770 MPa (i.e. 1.77×10¹⁰dynes/cm²).

The conformability of Example 12 was evaluated using the previouslydescribed tensile set test method. The % tensile set was 31.5%.

Multilayer Films

A multilayer film, Example 14, was prepared having two layers. The firstlayer was the same composition as Example 12 and had a thickness of 3mils. The second layer was a (heat bondable) composition having athickness of 3.5 mils having the following composition.

B60H IOA AA H Irg 651 DPA 79.2% 8.8% 8.8% 0.3% 2.9%The second layer was coated and on the cured first layer. Both filmlayers were cured with UVA light in the same manner as previouslydescribed. The multilayer film was subjected to the same testspreviously described. The test results were as follows:

-   Tensile Strength: 3200 psi-   Elongation at Break: 210%-   Youngs Modulus: 81,500 psi (555 MPa)-   Tg of cured (heat bondable) second film layer=−32.6° C.-   Tg of cured first film layer=41.9° C.

The morphology, transmission, haze, and clarity of some representativefilm examples were evaluated using the following test methods. The testresults are reported in Table 6 below.

Transmission, Haze and Clarity were measured using a BYK Haze-gard plus,CAT #4725.

Morphology Characterization by Transmission Electron Microscopy (TEM)

Analytical characterization of the sample morphology was carried out bytransmission electron microscopy (TEM). All the film samples were imagedin cross-section.

Sample Preparation

The film samples were prepared using room-temperature ultramicrotomy asfollows: 1) roughly ¼″ by ½″ sections were cut from the film samplesusing a scalpel blade. These sections were embedded in Scotchcast #5electrical resin. The embedded samples were allowed to room-temperaturecure overnight; 2) thin slices of the embedded film (in cross-section)were cut by ultramicrotomy (Leica FC7) using a diamond knife. Slicethickness varied from 110 nm to 150 nm, depending on the sample. Cuttingspeed was 0.15 mm/sec; 3) the thin slices were floated ontodistilled/deionized water, and then collected onto a standard TEM samplegrid: A carbon/formvar film supported on a 3 mm diameter, 150 mesh Cugrid.

Imaging

The prepared thin sections were imaged by TEM (FEI Osiris, 200 kv fieldemission TEM). Magnification range was from 450× to 20,000× (instrumentmagnification). Various imaging modes were employed to characterize themorphology. They are briefly described below:

TEM: Conventional Transmission Electron Microscopy is a microscopytechnique in which a beam of electrons is transmitted through anultra-thin specimen, in this case 110-150 nm, interacting with thespecimen as it is transmitted through. An image is formed as a result ofthe electron/sample interactions. At the lower magnifications used here,TEM image contrast is primarily due to the variations in the thickness,structure and composition in the material.

STEM: Scanning Transmission Electron Microscopy. An alternate mode ofimaging in the TEM: In this case the electron beam is rastered in muchthe same way as in an SEM image, but with a significantly smaller probesize. Probe size for this imaging mode ranges from 0.5 nm to 5 nm.

HAADF: High Angle Annular Dark Field imaging mode. HAADF images areformed by collecting the scattered (vs. transmitted) electrons with anannular dark-field detector. The high angle, incoherently scatteredelectrons which form the image are highly sensitive to variations in theaverage atomic number, thus the contrast in these images iscompositionally sensitive. The HAADF imaging mode is also known asZ-contrast imaging.

TABLE 6 Example Transmission Haze Clarity Morphology by TEM AnalysisControl A 94.6 11.1  91.6 Single phase  8 94.6  8.17 90.4 Single phase11 94.6  2.39 94.5 Single phase

What is claimed is:
 1. A film comprising at least one layer formed froma film composition comprising: a (meth)acrylic polymer and polyvinylacetal resin comprising polymerized units having the following formula

wherein R₁ is hydrogen or a C1-C7 alkyl group; and at least 10 wt-% ofpolymerized units of monofunctional alkyl (meth)acrylate monomer havinga glass transition temperature (Tg) of less than 0° C.; wherein the filmhas a single phase and a glass transition temperature (Tg) in the rangeof 30° C. to 60° C.
 2. The film of claim 1 wherein the film compositioncomprises no greater than 60 wt-% of polymerized units of monofunctionalalkyl (meth)acrylate monomer having a Tg of less than 0° C.
 3. The filmof claim 1 wherein the monofunctional alkyl (meth)acrylate monomer has aTg of less than −10° C.
 4. The film of claim 1 wherein the filmcomposition comprises a bio-based content of at least 10% of the totalcarbon content.
 5. The film of claim 1 wherein the film compositioncomprises polymerized units of an alkyl (meth)acrylate monomer having analkyl group with 8 carbon atoms.
 6. The film of claim 1 wherein the filmcomposition further comprises up to 35 wt-% of polymerized units of amonofunctional alkyl (meth)acrylate monomer having a Tg greater than 40°C.
 7. The film of claim 1 wherein the film composition further comprisesat least 10 wt-% and no greater than 65 wt-% of polymerized units ofpolar monomers.
 8. The film of claim 7 wherein the polar monomers areselected from the group consisting of acid-functional, hydroxylfunctional monomers, nitrogen-containing monomers, and combinationsthereof.
 9. The film of claim 1 wherein the film composition comprisespolyvinyl butyral.
 10. The film of claim 1 wherein the film compositioncomprises 5 to 30 wt-% of polyvinyl acetal resin.
 11. The film of claim1 wherein the polyvinyl acetal resin has a polyvinyl alcohol content inthe range of 10 to 30 wt-%.
 12. The film of claim 1 wherein thepolyvinyl acetal resin has a glass transition temperature in the rangeof 60° C. to 75° C.
 13. The film of claim 1 wherein the polyvinyl acetalresin has an average molecular weight (Mw) in the range of 20,000 g/moleto 75,000 g/mole.
 14. The film of claim 1 wherein the film compositionfurther comprises polymerized units of a multifunctional crosslinkerwherein the crosslinker comprises functional groups selected from(meth)acrylate, alkenyl, and hydroxyl-reactive groups.
 15. The film ofclaim 1 wherein the film composition further comprises additives in anamount no greater than 25 wt-%.
 16. The film of claim 1 wherein the filmcomposition further comprises a photoinitiator.
 17. The film of claim 1wherein the film composition comprises no greater than 10 wt-% ofpolymerized units of methacrylate monomers.
 18. The film of claim 1wherein the (meth)acrylic polymer is a random copolymer.
 19. The film ofclaim 1 wherein the film is a monolithic film.
 20. The film of claim 1wherein the film is a film layer of a multilayer film.
 21. The film ofclaim 20 wherein the multilayer film further comprises a second filmlayer, the second film layer comprising a (meth)acrylic polymer andpolyvinyl acetal resin wherein the second film layer has a Tg of lessthan 30° C.
 22. The film of claim 21 wherein the second film layer isheat bondable.
 23. The film of claim 1

wherein the film has a gel content of at least 20%.
 24. The film ofclaim 1 wherein the film has an elongation at break of at least 175%.25. The film of claim 1 wherein the film has a tensile strength asdetermined by ASTM D-882-10 at a rate of 300 mm/minute in the range of10 MPa to 50 MPa.
 26. The film of claim 1 wherein the film exhibits a180 degree peel adhesion to glass of 2 oz/inch or less at a 12inch/minute peel rate.